Therefore it will be maintained by many that such lectures produce more evil than good, creating as they do, and augmenting, that dilettanteism from which our period is already suffering. In our schools also this dilettanteism is gaining such dimensions, that one might get thoroughly frightened at the immoderate expansion of young people's knowledge, were it not for its small depth, which lessens the danger, and for the fact that the forgetting keeps pace with the learning. Accept my open avowal, that I also am unable to invalidate the objection that popular lectures on scientific subjects are not able to impart a really competent knowledge, and do not form experts.
But I believe that this does not matter, and that they have no such purpose. They are neither an exhaustive, scientific, nor a practical instruction, but a scientific edification and elevation, which are to raise our minds and hearts, and to affect us like listening to good music—to a symphony, the purpose of which is certainly not to make musicians of all the listeners. It is sufficient to feel the harmony which lies in the nature of good music. There is harmony in all our knowing and doing, our aiming and striving, as far as there is truth in them, and fortunately the sense for perceiving this harmony is as widely spread among mankind as the sense for music. This harmony, which pervades every truth, ought to be brought home to the consciousness and feelings of everybody, so that the greatest number may rejoice and become interested in it, that we may approach new subjects, and perhaps make them our study, or that, at all events, knowledge and resulting sympathy may induce us to lend our help to those men whose profession and calling require them to enter more minutely and exactly into the subjects in question. In this respect popular lectures have a high and serious mission. It is their mission to create correct general ideas, to facilitate our grasp of them, to awaken and spread a certain love for different tasks of mankind and of the period, to form ties of friendship between things, ideas, and men. Sympathy and sacrifices cannot be expected or asked from us, if their objects are unknown to or badly understood by us.
For these reasons it is my desire to awaken your interest for some subjects relating to hygiene, and particularly to impress upon you most vividly how much in this respect remains to be done and created, a work we all ought to take our share in.
One of the incessant wants of man is air.
We want air mainly to nourish us and to keep us cool. The quantity of air inhaled and exhaled by an adult in twenty-four hours amounts on an average to about 360 cubic feet, or 2,000 gallons. What we take in and give out during twenty-four hours, in the shape of solid and liquid food, occupies on an average the space of 52 pints, which is equal to 3000 of the volume of the air passing through our lungs. It will astonish you to hear, perhaps, for the first time that this amounts to 730,000 gallons in one year, and to be reminded of